Washington State Department of Transportation: I-5 Steilacoom-DuPont Rd to Thorne Lane-Corridor Improvements

Washington State DOT improved mobility, opened up commuting options, and improved safety through its $243 million I-5 Steilacoom-DuPont Road to Thorne Lane-Corridor Improvements project.

I-5 is a national highway of strategic importance, moving goods and people between two borders, linking major cities, and serving as a critical corridor for military use. Beginning in the 1990s, traffic studies indicated that High Occupancy Vehicle or HOV lanes on I-5 would be required through Pierce County in the future. As a point of reference, traffic on I-5 had increased noticeably through the Joint Base Lewis-McChord corridor over the previous decade.

The project rebuilt the I-5 interchanges at Thorne Lane and Berkeley Street to create room for HOV lanes and auxiliary lanes. The improvements have drastically improved travel times, reduced maintenance costs, and improved safety. The interchanges support travel for people walking and rolling, while improving last mile travel for future transit development. Multipurpose paths provide connectivity across I-5.The Thorne Lane interchanges used roundabouts to keep travelers moving and reduce travel times. A shared exit on southbound I-5 to Thorne Lane and Berkeley Street creates an auxiliary lane and reduces potential collisions caused by excessive merging between travel lanes.